NOTES: New Perspectives in the Classification of the Flavobacteria: Description of Chryseobacterium gen. nov., Bergeyella gen. nov., and Empedobacter nom. rev.

This 1994 paper revises the classification of Flavobacterium species using genotypic, chemotaxonomic, and phenotypic data, particularly rRNA-DNA hybridization analysis. The authors identified that six misclassified Flavobacterium species—F. balustinum, F. gleum, F. indologenes, F. indoltheticum, F. meningosepticum, and F. scophthalmum—form a distinct phylogenetic group and establish the new genus Chryseobacterium, with C. gleum as the type species. Another misclassified organism, Weeksella zoohelcum, is transferred to a new genus, Bergeyella. The genus Empedobacter is revived to accommodate F. breve as E. brevis. Importantly, Flavobacterium aquatile is retained as the only species in the original genus Flavobacterium. The authors justify these changes based on divergence levels in rRNA melting temperatures—differences exceeding the typical 4-7°C range within genera indicate separate generic status. The study demonstrates how phylogenetic analysis combined with classical biochemical features (quinone content, fatty acid profiles, phenotypic characteristics) can clarify taxonomy in poorly defined bacterial groups.

Key findings

• Six formerly misclassified Flavobacterium species form a tight rRNA cluster and are reclassified into the new genus Chryseobacterium with Chryseobacterium gleum as the type species.
• Weeksella zoohelcum is transferred to a new genus, Bergeyella zoohelcum, based on distinct phenotypic and genotypic characteristics including different fatty acid profiles and urea activity.
• The genus Empedobacter is revived to accommodate Flavobacterium breve as Empedobacter brevis, which is genotypically distinct from both the Chryseobacterium group and other Flavobacterium species.
• Flavobacterium aquatile remains as the sole species in the genus Flavobacterium, though its original strain is unrepresentative of the genus description.
• The reclassification is justified using polyphasic taxonomy integrating rRNA-DNA hybridization data, menaquinone content (primarily MK-6), fatty acid profiles, and classical phenotypic characteristics.